(a) Field of the Invention
This invention relates to the hydrofracturing of an underground aquifer from a water well borehole and more particularly, but not by way of limitation, to hydrofracturing a specific interval or zone in a aquifer from the water well borehole and introducing gravel proppants under pressure for increasing water flow production from the water well.
(b) Discussion of Prior Art
Along the front range of the Rocky Mountains in Colorado, the Denver Basin aquifers are a major source of water supply for the Denver metropolitan area. As the cost of drilling and equipping water wells increases, combined with the naturally low transmissive water-bearing materials of these aquifers, new methods for increasing the production of well yields and extending the sustainable life of water wells need to be developed. Each of the Denver Basin aquifers is comprised of several sandstone and siltstone layers. Within each of the aquifers, these water-bearing intervals vary in thickness, hydraulic conductivity, storage coefficients and yield. Therefore, to enhance or stimulate additional production or yield from any of the aquifers is difficult due to the characteristics of the individual aquifers.
Heretofore, most attempts to increase low yields and mitigate the sustainability problems have been focused on wellhead treatments subsequent to drilling and equipping the well. Mechanical and chemical treatments have been used to increase the efficiency of the well and rehabilitate the aquifer at or in the immediate area, less than a few feet, of the well borehole annulus. While these treatments have variable results, sometimes increasing the well production by a certain percentage, typically less than a 50% increase from the current well production, the improvements typically are temporary with well yields decreasing over time to at or below the original yields determined after the initial completion of the well.
Recent attempts to increase yields and improve sustainability in water wells on a long-term basis have employed oil field technologies. These attempts involved directional drilling techniques and completions, as well as well bore hydrofracturing. Two wells in the Denver Basin have employed directional drilling techniques to enhance the well production. Both have showed limited, if any, success. The cost/benefit ratios using directional drilling techniques have not been favorable. One well showed only marginal production results, while costs of the well completion were two to three time the normal cost for a standard vertical well completion. The second directionally-drilled well in the Denver Basin involved the drilling of one vertical well and a second directionally-drilled well to intercept the first vertical well. Due to several technical problems, the directionally-drilled well was abandoned and the vertical well, although damaged due to the attempted dual-well completion technique, produced lower than anticipated yields. The cost of the second directionally-drilled well was three to five times the normal well completion costs for a standard vertically-completed well.
In addition to the above-mentioned directionally-drilled wells, one deep Denver Basin well was recently hydrofractured using modified oil field techniques by the inventor of the subject process described herein. The hydrofracturing was completed in one operation over an entire length of an aquifer formation, which included several non-saturated intervals. The success of this fracing process was limited due to the inability to control the process over certain specific saturated water producing intervals. While this process increased the initial production characteristics of the well, when the water that was injected into the well during the fracturing process was pumped out of the well, the long-term well yield was not increased.
None of the above mentioned attempts to improve and increase water well production in an underground aquifer, such as in the Denver Basin, provide the unique steps described herein for hydrofracing a specific interval using high water pressure with gravel proppants for increased water production for long-term well yield.